Modern storage media includes not only media that store data in a physically sequential manner, such as traditional magnetic and optical storage media, but also media that store data in a physically random manner, such as solid-state based storage media. Such physically random media allow any one block of data to be accessed as efficiently as any other block of data. These, and other, physical differences between the various storage media commonly available today result in storage media that differ in capability, attributes and performance. For example, magnetic and optical media require a reading and writing apparatus that physically moves from the physical location of the device head to the physical location of a block. Consequently, the speed with which such storage media can read or write data is dependent upon the proximity of the locations of the data on the media, since the device head must physically transition from one location to the other. Conversely, solid-state based storage media can read and write data through electrical signals without requiring any physically moving parts. As a result, the data stored on such media can be written, or read, with efficiency that is not dependent upon the particular location of the data on, for example, rotating media.
From the perspective of a user of such storage media, magnetic and optical storage media that store data in a sequential manner are generally regarded as having specific capability, attribute and performance advantages and disadvantages with respect to solid-state based storage media. For example, magnetic media is generally regarded as having a greater density per unit of area than solid state media. As a result, magnetic media can store between three to five times more information than solid-state media within a given physical area. Similarly, magnetic storage media are generally regarded as being able to write a large amount of data in a sequential manner faster than solid-state based storage media, again due to the sequential nature of magnetic storage media. By contrast solid-state based storage media are generally regarded as being able to read and write small amounts of randomly addressed data, in a substantially faster manner than magnetic or optical storage media.
Among attribute differences, solid-state based storage media are generally regarded as being quieter than magnetic-based storage media, since, as indicated previously, solid-state media can comprise no moving parts. Solid-state based media are also generally regarded as being more power efficient and consuming less power than magnetic-based storage media.
One capability difference between solid-state based storage media and magnetic and optical storage media that can have a substantial impact on the user of such storage media is the reliability of such storage media. Traditional magnetic media is generally considered to have a substantial usage period between failures. From the user's perspective, such media can be written repeatedly without special consideration being paid to wear or data loss, except, of course, in statistically rare mechanical failures. Solid-state based storage media, on the other hand, are generally considered to have a limited number of writes before their physical nature can result in data loss at an individual bit level. Techniques such as “wear leveling” can be utilized to prevent prematurely excessive utilization of portions of such solid-state based storage media, but such wear leveling techniques can have a performance impact.
Modern storage devices including both sequential based storage media devices, and solid-state based storage media devices, traditionally comprise, in addition to the storage media itself, one or more capable controllers, which are designed to manage the data stored on the storage media itself. These controllers can perform management tasks that are internal to the storage device itself, such as, for example, compaction, encryption and wear leveling.